BackService.java

package net.darkdna.amanda.things.thingy.rpi;

import android.app.Service;
import android.content.Intent;
import android.graphics.PixelFormat;
import android.os.Binder;
import android.os.IBinder;
import android.util.Log;
import android.view.Gravity;
import android.view.InputDevice;
import android.view.KeyEvent;
import android.view.MotionEvent;
import android.view.View;
import android.view.WindowManager;
import android.widget.ImageView;

import com.google.android.things.userdriver.InputDriver;
import com.google.android.things.userdriver.UserDriverManager;

/**
 * Created by amanda on 1/1/17.
 */
public class BackService extends Service {
    private static final String TAG = BackService.class.getSimpleName();
    private static final int KEY_CODE = KeyEvent.KEYCODE_ESCAPE;

    private WindowManager mWindowManager;
    private ImageView mBackButton;
    private InputDriver mDriver;


    private BackBinder mBinder = new BackBinder();

    public class BackBinder extends Binder {
        private BackBinder() {
        }

        public void showButton() {
            Log.d(TAG, "showButton()");

            if (mBackButton == null) {
                Log.w(TAG, "mBackButton is null.");
                return;
            }

            WindowManager.LayoutParams layoutParams = new WindowManager.LayoutParams(
                    WindowManager.LayoutParams.WRAP_CONTENT,
                    WindowManager.LayoutParams.WRAP_CONTENT,
                    WindowManager.LayoutParams.TYPE_PHONE,
                    WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE,
                    PixelFormat.TRANSLUCENT);

            layoutParams.gravity = Gravity.BOTTOM | Gravity.START;
            layoutParams.x = 0;
            layoutParams.y = 0;

            mWindowManager.addView(mBackButton, layoutParams);
        }

        public void hideButton() {
            Log.d(TAG, "hideButton()");

            if (mBackButton == null) {
                Log.w(TAG, "mBackButton is null.");
                return;
            }

            mWindowManager.removeView(mBackButton);
        }
    }

    @Override
    public IBinder onBind(Intent intent) {
        return mBinder;
    }

    @Override
    public void onCreate() {
        super.onCreate();
        Log.d(TAG, "onCreate");

        mWindowManager = (WindowManager) getSystemService(WINDOW_SERVICE);

        mDriver = InputDriver.builder(InputDevice.SOURCE_CLASS_BUTTON)
                .setName("BackService")
                .setVersion(1)
                .setKeys(new int[]{KEY_CODE})
                .build();

        UserDriverManager.getManager().registerInputDriver(mDriver);

        mBackButton = new ImageView(this);
        mBackButton.setBackgroundColor(0xDD000000);
        mBackButton.setImageResource(android.R.drawable.ic_media_previous);

        mBackButton.setOnTouchListener(new View.OnTouchListener() {
            @Override
            public boolean onTouch(View v, MotionEvent event) {
                if(v != mBackButton) {
                    return false;
                }

                Log.d(TAG, "mBackButton pressed.");
                if (mDriver == null) {
                    Log.w(TAG, "mDriver is null.");
                    return false;
                }


                if (event.getAction() == MotionEvent.ACTION_DOWN) {
                    Log.d(TAG, "Action is ACTION_DOWN");

                    mDriver.emit(new KeyEvent[]{
                            new KeyEvent(KeyEvent.ACTION_DOWN, KEY_CODE),
                    });

                    return true;
                } else if (event.getAction() == MotionEvent.ACTION_UP) {
                    Log.d(TAG, "Action is ACTION_UP");

                    mDriver.emit(new KeyEvent[]{
                            new KeyEvent(KeyEvent.ACTION_UP, KEY_CODE),
                    });

                    return true;
                }

                Log.w(TAG, "Unknown action.");
                return false;
            }
        });
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        Log.d(TAG, "onDestroy");

        if (mDriver != null) {
            UserDriverManager.getManager().unregisterInputDriver(mDriver);
        }

        mBinder.hideButton();
    }
}